Hydroxyacrylic modified inks

ABSTRACT

The invention is water-based printing inks and coatings formulated with stable low viscosity grind bases made from modified rosin grinding resins. These grinding resins are produced via the fusion esterification of fortified rosin with hydroxyacrylic resins and various polyols. Suitable hydroxyacrylic resins are prepared by copolymerizing an hydroxyalkylacrylate or methacrylate with alkyl acrylates, cycloalkyl acrylates, methacrylates, or styrene. These hydroxyacrylic resins can be made to contain a wide range of molecular weights and hydroxyl contents, thereby permitting formulation of a wide variety of soluble grinding resins and printing inks.

This application is a continuation-in-part of our commonly assigned,allowed, co-pending U.S. patent application Ser. No. 07/923,543 filedAug. 3, 1992, entitled "Hydroxyacrylic Modified Rosin Resins ForWater-Based Coatings"; which, in turn, was a continuation-in-part ofU.S. patent application Ser. No. 07/796,651 filed Nov. 22, 1991, andexpressly abandoned on Aug. 14, 1992.

FIELD OF INVENTION

This invention relates to novel water-based inks and coatings formulatedutilizing grind bases produced from hydroxyacrylic modified rosin baseink pigment grinding resins.

BACKGROUND OF THE INVENTION

Impelled by environmental concerns and increasing governmentalregulations on the volatile organic content of coatings, theapplications of water-based flexographic and rotogravure inks areincreasing in the ink industry. A typical water-based ink system isformulated by the addition of a binder resin (usually acrylic polymerlatices) to a grind base. Grind bases are prepared by using grindingresins to disperse pigments. Pigments are crystalline solids composed ofagglomerates, aggregates, and primary particles which vary in size from0.02 to 0.50 microns. During the grinding process, agglomerates andaggregates are broken down into primary particles which possess strongtendencies to reassociate in a ink. The finer the particle size of thepigment, the greater the color strength, but the more difficult thepigment becomes to disperse. Grinding resins help prevent the particlesfrom reassociating by increasing both the electrostatic and stericrepulsion between pigment particles.

An ink formulator must consider the compatibility of the various inkcomponents when selecting the grind resins to be used. Grind bases(i.e., pigment dispersions) are let down with a variety ofalkali-soluble resins or alkali-insoluble resin emulsions to achieve theproperties desired for the end use of the ink. If the grind resins andthe let-down resins are not compatible, the result may be pigmentflocculation, viscosity increase, loss of color strength, and otherproblems.

Soluble maleic resins have been used for several years in water-basedinks and coatings. Typically these resins are partial esters of maleatedor fumarated rosin with various polyols having acid numbers greater than140. However, when used in aqueous pigment grinding media, thesetraditional maleic resins exhibit a major shortcoming--the viscositiesof the resultant pigment dispersions tend to be unstable over time.

It is known to correct this problem by modifying maleic resins withstyrene-allyl alcohol (SAA) copolymer, thereby producing pigment grindswith stable viscosities. SAA is a hard (softening point of 95-110° C.)thermoplastic, low molecular weight polymer manufactured by the MonsantoCorporation. However, SAA copolymers have two significantdisadvantages: 1) they are relatively expensive, and 2) they arecurrently commercially available in only two grades--RJ-100 (which has amolecular weight of 2340) and RJ-101 (which has a molecular weight of1700). Thus, the range of maleic resins which may be formulatedutilizing SAA is severely limited.

Therefore, it is the object of this invention to formulate water-basedinks and coatings containing stable viscosity pigment grinds producedfrom soluble maleic grinding resins which are not SAA modified.

SUMMARY OF THE INVENTION

The object of this invention is met by replacing traditional SAA resinswith hydroxyacrylic resins in an esterification reaction with fumaratedor maleated rosin and a polyol. The hydroxyacrylic resins are producedby copolymerizing an hydroxy-alkylacrylate or methacrylate with alkylacrylates, cycloalkyl acrylates, methacrylates, or styrene. In additionto being relatively inexpensive to make, such hydroxyacrylic resins canbe prepared to contain a wide range of molecular weights and hydroxylcontents. This versatility allows formulation of a wide variety ofsoluble maleic resins capable of being used as grind resins or let downresins for water-based ink vehicles and inks.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The process for producing the desired maleic resin comprises reacting ina fusion esterification reaction: 70-96% by weight of fumarated rosin,maleated rosin, or combinations thereof; 2-18% by weight of a polyol orcombination of polyols; and 2-20% by weight of a hydroxyacrylic resin orcombination of hydroxyacrylic resins. The resulting maleic resin may beutilized as a grind resin or as a let down resin, depending upon therequirements of the coating formulator.

Rosins which are suitable for use in the reaction include, but are notlimited to, the following:

wood rosin,

tall oil rosin, and

gum rosin.

Tall oil rosin is preferred, more preferably fortified tall oil rosinmade by reacting the rosins with varying amounts of fumaric acid, maleicanhydride, or maleic acid. Fortification of rosin is well known in theart, as evidenced by U.S. Pat. No. 2,994,635, which is herebyincorporated by reference.

Polyols which are suitable for use in the reaction include, but are notlimited to, the following:

glycerol,

sorbitol,

pentaerythritol,

neopentyl glycol,

ethylene glycol,

diethylene glycol,

dipropylene glycol,

polyethylene glycol, and

combinations thereof.

Suitable polyethylene glycols and polyethylene glycol mixtures have amolecular weight in the range of 150-5,000.

Hydroxyacrylic resins suitable for use in formulating these maleicgrinding resins are produced by reacting in a free radical additionpolymerization reaction:

(a) 50.0-89.5 parts by weight of a member selected from the groupconsisting of styrene, alkyl acrylates, cycloalkyl acrylates,methacrylates, and combinations thereof where the alkyl or cycloalkylgroup contains 1-18 carbon atoms,

(b) 10.0-50.0 parts by weight of a hydroxy-containing monomer, orcombination of monomers, having the chemical structure: ##STR1## whereR₁ is a hydrogen or methyl group and R₂ is a C₂ -C₁₄ alkylene,

(c) 0.5-12.0 parts by weight of a peroxide or azo catalytic initiator,and

(d) up to 10.0 parts by weight of a mercaptan-containing chain transferagent.

Suitable hydroxyacrylic polymer resins have a molecular weight in therange of 1,000-5,000. Depending on the type of solvent employed in thepolymerization reaction, it may be necessary to add a chain transferagent to achieve the desired molecular weight. (For example, chaintransfer agents are not necessary when diethylene glycol, dipropyleneglycol, and similar solvents are utilized.) Chain transfer agents whichare suitable for use in the above reaction must contain a singlemercaptan group and include, but are not limited to, the following:

dodecyl mercaptan,

mercaptoacetic acid,

mercaptopropionic acid,

octyl mercaptan,

2-mercaptoethanol, and

combinations thereof.

Catalytic peroxide or azo initiators suitable for use in the abovereaction include, but are not limited to, the following:

azo-bis-isobutyonitrile,

benzoyl peroxide,

t-butyl peroctoate,

t-butyl peroxybenzoate, and

combinations thereof.

Solvents which are suitable for use in the polymerization reactioninclude, but are not limited to, the following:

methyl isobutyl ketone,

toluene,

ethanol,

isopropanol,

t-butanol,

diethylene glycol,

dipropylene glycol, and

combinations thereof.

In view of the teachings contained herein, it is well within the abilityof a skilled artisan to utilize these solvents to produce hydroxyacrylicresins and maleic resins having different viscosities and solids levels.For ease of manipulation, it is preferable to produce hydroxyacrylicresins having a 50-80% solids level.

As appreciated in the art, the exact components and properties ofcomponents desired for any given ink application can vary, and,therefore, routine experimentation may be required to determine theoptional components and proportions of components for a givenapplication and desired properties.

The following examples are provided to further illustrate the presentinvention and are not to be construed as limiting the invention in anymanner.

EXAMPLE 1

A hydroxyacrylic resin was produced via the following procedure. To a500-ml flask fitted with a mechanical stirrer, reflux condenser, and twoaddition funnels was charged 60 g of methyl isobutyl ketone (MIBK). Tothe first addition funnel was charged 56.5 g of styrene, 43.5 g of2-hydroxyethyl methacrylate, and 4.0 g of 2-mercaptoethanol. To thesecond addition funnel was added 20.0 g of MIBK and 2.0 g of t-butylperoxybenzoate. The flask was heated to reflux (110° C.), and thecontents of the two addition funnels were added concurrently over onehour. Refluxing was continued for three hours, after which a solution of20.0 g of MIBK and 2.0 g of t-butyl peroxybenzoate was added over tenminutes. Refluxing was continued for three more hours. The resultanthydroxyacrylic resin solution had a solids content of 54% and aGardner-Holt viscosity of J.

EXAMPLE 2

A hydroxyacrylic resin was produced via the following procedure. To a500-ml flask fitted with a mechanical stirrer, reflux condenser, and twoaddition funnels was charged 60 g of toluene. To the first additionfunnel was charged 45.5 g of styrene, 21.5 g of 2-ethylhexyl acrylate,33.0 g of 2-hydroxyethyl methacrylate, and 6.0 g of 2-mercaptoethanol.To the second addition funnel was added 20.0 g of toluene and 2.0 g oft-butyl peroxybenzoate. The flask was heated to reflux (110° C.), andthe contents of the two addition funnels were added concurrently overone hour. Refluxing was continued for three hours, after which asolution of 20.0 g of toluene and 2.0 g of t-butyl peroxybenzoate wasadded over ten minutes. Refluxing was continued for three more hours.The resultant acrylic resin solution (hereafter referred to ashydroxyacrylic resin no. 1) had a solids content of 53% and aGardner-Holt viscosity of K.

A series of hydroxyacrylic resins were prepared using the aboveprocedure wherein the composition of the resins and the solventsutilized were varied. The results are listed in Table I below.

                  TABLE I                                                         ______________________________________                                        Hydroxyacrylic Resins                                                         Resin                              Gardner-Holt                               No.   Composition*                                                                             Solvent    % Solids                                                                             Viscosity                                  ______________________________________                                        1     45.5 Styrene                                                                             Toluene    51.3   E                                                21.5 2-EHA                                                                    33.0 HEMA                                                                      6.0 2-ME                                                               2     45.5 Styrene                                                                             Ethanol    50.2   A                                                21.5 2-EHA                                                                    33.0 HEMA                                                                      6.0 2-ME                                                               3     45.5 Styrene                                                                             Isopropanol                                                                              49.9   E                                                21.5 2-EHA                                                                    33.0 HEMA                                                                      6.0 2-ME                                                               4     45.5 Styrene                                                                             t-Butanol  50.9    T+                                              21.5 2-EHA                                                                    33.0 HEMA                                                                      6.0 2-ME                                                               5     51.0 Styrene                                                                             Isopropanol                                                                              50.1   B-C                                              27.0 2-EHA                                                                    22.0 HEA                                                                       6.0 2-ME                                                               ______________________________________                                         *2-EHA = 2ethylhexyl acrylate                                                 HEA = hydroxyethyl acrylate                                                   HEMA = hydroxyethyl methacrylate                                              2ME = 2mercaptoethanol                                                   

A polymer-modified maleic rosin resin was produced via the followingprocedure. ROSIN SS (250.0 g) was melted in a 1000-ml three-necked,round-bottomed flask. (ROSIN SS is a tall oil based rosin manufacturedby Westvaco.) The flask was equipped with a Dean-Stark trap, condenser,nitrogen inlet, thermocouple, heating mantle, and heating tape. Fumaricacid (62.0 g) was added to the molten rosin at 150° C., and this mixturewas heated to 200° C. and stirred for three hours. Next, a blend oftriethylene glycol (17.5 g) and glycerol (10 g) was slowly added. Thereaction mixture was stirred for one hour, and then hydroxyacrylic resinno. 1 (84.9 g at 53% solids in toluene) was added. The reaction was thenheld at 210° C. for three hours to produce a polymer-modified rosinresin (hereafter referred to as maleic resin no 1).

A series of polymer-modified maleic rosin resins were prepared byfollowing the above procedure and substituting the respectivehydroxyacrylic resins listed in Table I. FILTREZ 5014® (a widely usedSAA-containing rosin resin manufactured by the Filtered Rosin ProductsCorporation) was employed as a control against which the maleic resinswere evaluated (via making different pH-level varnishes from theresins). The varnishes were made by mixing each respective maleic resin(35 parts), water (51.8 parts), isopropanol (7 parts), concentratedammonium hydroxide (6 parts), and FOAMBLAST 1005 (0.2 parts) in a WaringBlender. (FOAMBLAST 1005 is a defoaming agent manufactured by the RossChemical Company.) The varnishes were allowed to stand overnight to letthe air and foam dissipate. The results ar given in Table II below.

                  TABLE II                                                        ______________________________________                                        Maleic Resins                                                                                  Varnish                                                                                                Gardner-                                             Softening          %     Holt                                Resin No.                                                                             Acid No. Point, °C.                                                                       No.  pH  Solids                                                                              Viscosity                           ______________________________________                                        (Control)                                                                             171      143       A    8.2 35.4  Z5                                  Filtrez                    B    8.9 34.8  R-                                  5014                                                                          1       181      128       A    8.1 34.8  X-Y                                                            B    8.8 35.9  S+                                  2       150      138       A    8.2 35.0  Z                                                              B    8.8 34.0  M-N                                 3       169      131       A    8.2 35.1  X-Y                                                            B    8.7 34.5  N                                   4       178      139       A    8.1 34.0  Z2+                                                            B    8.8 35.4  N                                   5       181      132       A    8.3 34.7  F-G                                                            B    8.8 34.0  E                                   ______________________________________                                    

Half of the varnishes listed in Table II above (i.e., the B varnishes)were utilized to produce a series of grind bases via the procedures ofcombining 49.5 g of varnish, 50.0 g of phthalocyanine blue G.S.high-solids presscake (manufactured by Sun Chemical Company), and 0.5 gof FOAMBLAST 1005 in a Waring Blender. After five minutes ofpredispersion, the batch was poured in a "quicky mill" with 100.0 g ofshot and placed on a Red Devil paint shaker for one hour. The grindbases were evaluated for viscosity, and the results are shown in TableIII below.

                  TABLE III                                                       ______________________________________                                        Phthalo Blue Grind Bases                                                      Varnish Grind   Shell  Grind Base Viscosity (sec)                             From    Base    Cup    1          15   22                                     Resin No.                                                                             pH      No.    Day  8 Days                                                                              Days Days 29 Days                           ______________________________________                                        Control 8.8     3      19   22    30   27   24                                                4      15   17    15   18   16                                1B      8.6     3      64   77    77   74   92                                                4      37   43    46   61   76                                2B      8.7     3      47   81    69   120  85                                                4      36   48    47   60   78                                3B      8.5     3      68   72    86   92   >120                                              4      48   52    56   56   62                                4B      8.7     3      42   59    72   71   72                                                4      34   37    40   42   39                                5B      8.3     3      23   30    41   42   44                                                4      16   21    25   28   26                                ______________________________________                                    

Water-based inks for printing on paper were produced from the grindbases described in Table III using the following formulation:

    ______________________________________                                        Grind base         60 parts by weight                                         JONREZ E-2003      40 parts by weight.                                        ______________________________________                                    

(JONREZ E-2003 is an acrylic emulsion manufactured by Westvaco, Inc.)The hydroxyacrylic resin-based inks exhibited superior characteristicswhen compared to the SAA-containing control ink.

Water-based inks for printing on plastic film (such as polyethylene orpolyester) were also produced from the grind bases described in TableIII using the following formulation:

    ______________________________________                                        Grind base         55 parts by weight                                         JONREZ E-2050      48 parts by weight                                         JONREZ W-2320       5 parts by weight                                         Isopropyl alcohol   2 parts by weight.                                        ______________________________________                                    

(JONREZ E-2050 is an acrylic emulsion manufactured by Westvaco, Inc.JONREZ W-2320 is a wax emulsion manufactured by Westvaco, Inc.) Thesehydroxyacrylic resin-based inks exhibited superior characteristics whencompared to the SAA-containing control ink.

Thus, as indicated in Table I a variety of hydroxyacrylic resins can beproduced in a number of solvents by following the above procedures.These hydroxyacrylic resins can be utilized to produce maleic resins(Table II), grind bases (Table III), and printing inks which comparefavorably with their SAA-based counterparts.

EXAMPLE 3

A hydroxyacrylic resin was produced without employing a chain transferagent via the following procedure. To a 500-ml flask fitted with amechanical stirrer, reflux condenser, and an addition funnel was charged70.80 g of dipropylene glycol. To the addition funnel was charged 92.85g of styrene, 31.40 g of hydroxyethyl acrylate, 19.45 2-ethylhexylacrylate, and 11.50 g of t-butyl peroxybenzoate. The flask was heated to150° C., and the contents of the addition funnel was added over a periodof one hour. Heating was continued for at a temperature of 150° C. forfour hours, after which the resultant hydroxyacrylic resin solution wasallowed to cool.

A polymer-modified maleic rosin resin was produced using thishydroxyacrylic resin solution via the following procedure. To a 1000-mlthree-necked, round-bottomed flask equipped with a Dean-Stark trap,condenser, nitrogen inlet, thermocouple, heating mantle, and heatingtape was charged 400.0 g of ROSIN SS. The rosin was heated to 200° C.,at which time 102.0 g of fumaric acid and one drop of ANTIFOAM A wasadded to the rosin. (ANTIFOAM A is a defoaming agent manufactured by DowCorning, Inc.) This mixture was held at 200° C. and stirred for threehours, after which 16.0 g of glycerine was added. The reaction mixturewas stirred at 200° C. for one hour, at which time 84.0 g of thehydroxyacrylic resin solution was added. This reaction mixture was heldat 200° C. for four hours before cooling, thereby producing apolymer-modified rosin resin having an acid number of 188 and asoftening point of 132° C.

EXAMPLE 4

A hydroxyacrylic resin was produced without employing a chain transferagent via the following procedure. To a 500-ml flask fitted with amechanical stirrer, reflux condenser, and an addition funnel was charged56.00 g of diethylene glycol. To the addition funnel was charged 92.85 gof styrene, 31.70 g of hydroxyethyl acrylate, 19.45 2-ethylhexylacrylate, and 11.50 g of t-butyl peroxybenzoate. The flask was heated to150° C., and the contents of the addition funnel was added over a periodof one hour. Heating was continued for at a temperature of 150° C. forfour hours, after which the resultant hydroxyacrylic resin solution wasallowed to cool.

A polymer-modified maleic rosin resin was produced using thishydroxyacrylic resin solution via the following procedure. To a 1000-mlthree-necked, round-bottomed flask equipped with a Dean-Stark trap,condenser, nitrogen inlet, thermocouple, heating mantle, and heatingtape was charged 400.0 g of ROSIN SS. The rosin was heated to 200° C.,at which time 102.0 g of fumaric acid and one drop of ANTIFOAM A wasadded to the rosin. This mixture was held at 200° C. and stirred forthree hours, after which 16.0 g of glycerine was added. The reactionmixture was stirred at 200° C. for one hour, at which time 84.0 g of thehydroxyacrylic resin solution was added. This reaction mixture was heldat 200° C. for four hours before cooling, thereby producing apolymer-modified rosin resin having an acid number of 187 and asoftening point of 133° C.

Many modifications and variations of the present invention will beapparent to one of ordinary skill in the art in light of the aboveteachings. It is therefore understood that the scope of the invention isnot to be limited by the foregoing description, but rather is to bedefined by the claims appended hereto.

What is claimed is:
 1. A water-based ink comprising ink pigmentsdispersed with a grinding resin let down in a binder resin emulsion,wherein said grinding resin is the fusion esterification reactionproduct of:(a) 70 to 96% by weight of a member selected from the groupconsisting of fumarated rosin, maleated rosin, and combinations thereof;(b) 2 to 18% by weight of a polyol; and (c) 2 to 20% by weight of ahydroxyacrylic resin comprising the free radical addition polymerizationreaction product of:(1) 50.0-89.5 parts by weight of a member selectedfrom the group consisting of styrene, alkyl acrylate, cycloalkylacrylate, methacrylate, and combinations thereof, where the alkyl orcycloalkyl group contains 1-18 carbon atoms, (2) 10.0-50.0 parts byweight of a hydroxy-containing monomer, or combination of monomers,having the chemical structure: ##STR2## where R₁ is a hydrogen or methylgroup and R₂ is a C₂ -C₄ alkylene, (3) 0.5-12.0 parts by weight of aperoxide or azo catalytic initiator, and (4) up to 10.0 parts by weightof a mercaptan-containing chain transfer agent.
 2. The water-based inkof claim 1 wherein said grinding resin is the fusion esterificationreaction product of:(a) 79 to 90% by weight of a member selected fromthe group consisting of fumarated rosin, maleated rosin, andcombinations thereof; (b) 2 to 12% by weight of a polyol; and (c) 8 to12% by weight of a hydroxyacrylic resin comprising the free radicaladdition polymerization reaction product of:(1) 65.0-83.0 parts byweight of a member selected from the group consisting of styrene, alkylacrylate, cycloalkyl acrylate, methacrylate, and combinations thereof,where the alkyl or cycloalkyl group contains 1-18 carbon atoms, (2)15.0-35.0 parts by weight of a hydroxy-containing monomer, orcombination of monomers, having the chemical structure: ##STR3## whereR₁ is a hydrogen or methyl group and R₂ is a C₂ -C₄ alkylene, (3)2.0-10.0 parts by weight of a peroxide or azo catalytic initiator, and(4) up to 6.0 parts by weight of a mercaptancontaining chain transferagent.
 3. The water-based ink of claim 1 wherein said grinding resin isthe fusion esterification reaction product of:(a) 70 to 96% by weight ofa member selected from the group consisting of fumarated rosin, maleatedrosin, and combinations thereof; (b) 1 to 9% by weight of a polyolselected from the group consisting of pentaerythritol, glycerol,sorbitol, neopentyl glycol, ethylene glycol, and combinations thereof;(c) 1 to 9% by weight of polyethylene glycol having an average molecularweight in the range of 100-5,000; (d) 2 to 20% by weight of ahydroxyacrylic resin comprising the free radical addition polymerizationreaction product of:(1) 50.0-89.5 parts by weight of a member selectedfrom the group consisting of styrene, alkyl acrylate, cycloalkylacrylate, methacrylate, and combinations thereof, where the alkyl orcycloalkyl group contains 1-18 carbon atoms, (2) 10.0-50.0 parts byweight of a hydroxycontaining monomer, or combination of monomers,having the chemical structure: ##STR4## where R₁ is a hydrogen or methylgroup and R₂ is a C₂ -C₄ alkylene, (3) 0.5-12.0 parts by weight of aperoxide or azo catalytic initiator, and (4) up to 10.0 parts by weightof a mercaptan-containing chain transfer agent.
 4. The water-based inkof claim 1 wherein said polyol is a member selected from the groupconsisting of glycerol, sorbitol, pentaerythritol, neopentyl glycol,ethylene glycol, diethylene glycol, dipropylene glycol, polyethyleneglycol having an average molecular weight in the range of 100-5,000, andcombinations thereof.
 5. The water-based ink of claim 1 wherein saidhydroxyacrylic resin has a molecular weight in the range of 1,000 to5,000.
 6. The water-based ink of claim 1 wherein said peroxide or azocatalytic initiator is a member selected from the group consisting ofazo-bis-isobutyonitrile, benzoyl peroxide, t-butyl peroctoate, t-butylperoxybenzoate, and combinations thereof.
 7. The water-based ink ofclaim 1 wherein said chain transfer agent is a member selected from thegroup consisting of dodecyl mercaptan, mercaptoacetic acid,mercaptopropionic acid, octyl mercaptan, 2-mercaptoethanol, andcombinations thereof.